/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.flink.table.types.logical;

import org.apache.flink.annotation.PublicEvolving;
import org.apache.flink.table.api.ValidationException;
import org.apache.flink.util.Preconditions;

import java.util.Collections;
import java.util.List;
import java.util.Objects;
import java.util.Set;

/**
 * Logical type for a group of year-month interval types. The type must be parameterized to one of
 * the following resolutions: interval of years, interval of years to months, or interval of months.
 *
 * <p>An interval of year-month consists of {@code +years-months} with values ranging from {@code -9999-11}
 * to {@code +9999-11}. The value representation is the same for all types of resolutions. For example, an
 * interval of months of 50 is always represented in an interval-of-years-to-months format (with default
 * year precision): {@code +04-02}.
 *
 * <p>The serialized string representation is {@code INTERVAL YEAR(p)}, {@code INTERVAL YEAR(p) TO MONTH},
 * or {@code INTERVAL MONTH} where {@code p} is the number of digits of years (=year precision).
 * {@code p} must have a value between 1 and 4 (both inclusive). If no year precision is specified,
 * {@code p} is equal to 2.
 *
 * <p>A conversion from and to {@code int} describes the number of months. A conversion from
 * {@link java.time.Period} ignores the {@code days} part.
 *
 * @see DayTimeIntervalType
 */
@PublicEvolving
public final class YearMonthIntervalType extends LogicalType {

	public static final int MIN_PRECISION = 1;

	public static final int MAX_PRECISION = 4;

	public static final int DEFAULT_PRECISION = 2;

	private static final String YEAR_FORMAT = "INTERVAL YEAR(%d)";

	private static final String YEAR_TO_MONTH_FORMAT = "INTERVAL YEAR(%d) TO MONTH";

	private static final String MONTH_FORMAT = "INTERVAL MONTH";

	private static final Set<String> NULL_OUTPUT_CONVERSION = conversionSet(
		java.time.Period.class.getName(),
		Integer.class.getName());

	private static final Set<String> NOT_NULL_INPUT_OUTPUT_CONVERSION = conversionSet(
		java.time.Period.class.getName(),
		Integer.class.getName(),
		int.class.getName());

	private static final Class<?> DEFAULT_CONVERSION = java.time.Period.class;

	/**
	 * Supported resolutions of this type.
	 *
	 * <p>Note: The order of this enum reflects the granularity from coarse to fine.
	 */
	public enum YearMonthResolution {
		YEAR,
		YEAR_TO_MONTH,
		MONTH
	}

	private final YearMonthResolution resolution;

	private final int yearPrecision;

	public YearMonthIntervalType(boolean isNullable, YearMonthResolution resolution, int yearPrecision) {
		super(isNullable, LogicalTypeRoot.INTERVAL_YEAR_MONTH);
		Preconditions.checkNotNull(resolution);
		if (resolution == YearMonthResolution.MONTH && yearPrecision != DEFAULT_PRECISION) {
			throw new ValidationException(
				String.format(
					"Year precision of sub-year intervals must be equal to the default precision %d.",
					DEFAULT_PRECISION));
		}
		if (yearPrecision < MIN_PRECISION || yearPrecision > MAX_PRECISION) {
			throw new ValidationException(
				String.format(
					"Year precision of year-month intervals must be between %d and %d (both inclusive).",
					MIN_PRECISION,
					MAX_PRECISION));
		}
		this.resolution = resolution;
		this.yearPrecision = yearPrecision;
	}

	public YearMonthIntervalType(YearMonthResolution resolution, int yearPrecision) {
		this(true, resolution, yearPrecision);
	}

	public YearMonthIntervalType(YearMonthResolution resolution) {
		this(resolution, DEFAULT_PRECISION);
	}

	public YearMonthResolution getResolution() {
		return resolution;
	}

	public int getYearPrecision() {
		return yearPrecision;
	}

	@Override
	public LogicalType copy(boolean isNullable) {
		return new YearMonthIntervalType(isNullable, resolution, yearPrecision);
	}

	@Override
	public String asSerializableString() {
		return withNullability(getResolutionFormat(), yearPrecision);
	}

	@Override
	public boolean supportsInputConversion(Class<?> clazz) {
		return NOT_NULL_INPUT_OUTPUT_CONVERSION.contains(clazz.getName());
	}

	@Override
	public boolean supportsOutputConversion(Class<?> clazz) {
		if (isNullable()) {
			return NULL_OUTPUT_CONVERSION.contains(clazz.getName());
		}
		return NOT_NULL_INPUT_OUTPUT_CONVERSION.contains(clazz.getName());
	}

	@Override
	public Class<?> getDefaultConversion() {
		return DEFAULT_CONVERSION;
	}

	@Override
	public List<LogicalType> getChildren() {
		return Collections.emptyList();
	}

	@Override
	public <R> R accept(LogicalTypeVisitor<R> visitor) {
		return visitor.visit(this);
	}

	@Override
	public boolean equals(Object o) {
		if (this == o) {
			return true;
		}
		if (o == null || getClass() != o.getClass()) {
			return false;
		}
		if (!super.equals(o)) {
			return false;
		}
		YearMonthIntervalType that = (YearMonthIntervalType) o;
		return yearPrecision == that.yearPrecision && resolution == that.resolution;
	}

	@Override
	public int hashCode() {
		return Objects.hash(super.hashCode(), resolution, yearPrecision);
	}

	// --------------------------------------------------------------------------------------------

	private String getResolutionFormat() {
		switch (resolution) {
			case YEAR:
				return YEAR_FORMAT;
			case YEAR_TO_MONTH:
				return YEAR_TO_MONTH_FORMAT;
			case MONTH:
				return MONTH_FORMAT;
			default:
				throw new UnsupportedOperationException();
		}
	}
}
